This function should be called by fs-dax file systems after opening the
devdax device. This adds holder_operations, which effects exclusivity
between callers of fs_dax_get().
This function serves the same role as fs_dax_get_by_bdev(), which dax
file systems call after opening the pmem block device.
This also adds the CONFIG_DEV_DAX_IOMAP Kconfig parameter
Signed-off-by: John Groves <john@xxxxxxxxxx>
---
drivers/dax/Kconfig | 6 ++++++
drivers/dax/super.c | 30 ++++++++++++++++++++++++++++++
include/linux/dax.h | 5 +++++
3 files changed, 41 insertions(+)
diff --git a/drivers/dax/Kconfig b/drivers/dax/Kconfig
index a88744244149..b1ebcc77120b 100644
--- a/drivers/dax/Kconfig
+++ b/drivers/dax/Kconfig
@@ -78,4 +78,10 @@ config DEV_DAX_KMEM
Say N if unsure.
+config DEV_DAX_IOMAP
+ depends on DEV_DAX && DAX
+ def_bool y
+ help
+ Support iomap mapping of devdax devices (for FS-DAX file
+ systems that reside on character /dev/dax devices)
endif
diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index aca71d7fccc1..4b55f79849b0 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -122,6 +122,36 @@ void fs_put_dax(struct dax_device *dax_dev, void *holder)
EXPORT_SYMBOL_GPL(fs_put_dax);
#endif /* CONFIG_BLOCK && CONFIG_FS_DAX */
+#if IS_ENABLED(CONFIG_DEV_DAX_IOMAP)
+/**
+ * fs_dax_get()
+ *
+ * fs-dax file systems call this function to prepare to use a devdax device for
+ * fsdax. This is like fs_dax_get_by_bdev(), but the caller already has struct
+ * dev_dax (and there * is no bdev). The holder makes this exclusive.
+ *
+ * @dax_dev: dev to be prepared for fs-dax usage
+ * @holder: filesystem or mapped device inside the dax_device
+ * @hops: operations for the inner holder
+ *
+ * Returns: 0 on success, <0 on failure
+ */
+int fs_dax_get(struct dax_device *dax_dev, void *holder,
+ const struct dax_holder_operations *hops)
+{
+ if (!dax_dev || !dax_alive(dax_dev) || !igrab(&dax_dev->inode))
+ return -ENODEV;
+
+ if (cmpxchg(&dax_dev->holder_data, NULL, holder))
+ return -EBUSY;
+
+ dax_dev->holder_ops = hops;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(fs_dax_get);
+#endif /* DEV_DAX_IOMAP */
+
enum dax_device_flags {
/* !alive + rcu grace period == no new operations / mappings */
DAXDEV_ALIVE,
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 9d3e3327af4c..4a86716f932a 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -57,6 +57,11 @@ struct dax_holder_operations {
#if IS_ENABLED(CONFIG_DAX)
struct dax_device *alloc_dax(void *private, const struct dax_operations *ops);
+
+#if IS_ENABLED(CONFIG_DEV_DAX_IOMAP)
+int fs_dax_get(struct dax_device *dax_dev, void *holder, const struct dax_holder_operations *hops);
+struct dax_device *inode_dax(struct inode *inode);
+#endif
void *dax_holder(struct dax_device *dax_dev);
void put_dax(struct dax_device *dax_dev);
void kill_dax(struct dax_device *dax_dev);
--
2.43.0
